The present invention generally relates to packaging and more particularly to a process for making unitary packages which hold a plurality of components, each package containing a load wrapped in a web of stretched collapsed film which forms a Z-shaped net-like configuration on the load.
Case packing or boxing is a common way of shipping multiple unit products. The multiple unit products are generally stacked in a corrugated box or are wrapped with kraft paper with the ends of the kraft paper being glued or taped. Another way of shipping such products is by putting a sleeve or covering of heat shrinkable film around the products and shrinking it to form a unitized package. The use of heat shrinkable film is described in U.S. Pat. Nos. 3,793,798; 3,626,654; 3,590,509; and 3,514,920. A discussion of this art is set forth in U.S. Pat. No. 3,867,806.
The present invention provides a simple and reliable process for wrapping a load of stacked multiple unit products into a single wrapped package load by using a single strand of stretched overwrap material formed into a specifically shaped configuration around the load allowing the contents of the load to breathe.
When the present process is compared with other processes currently used to pack products in corrugated boxes and the cost of the corrugated boxes themselves, the invention shows an enormous cost savings. In addition to these factors the invention uses stretch. film material, which is less expensive than netting material or perforated stretch film and which also provides product visibility not possible with kraft or corrugated wrapping plus the desirable feature of letting the load "breathe." This feature is especially desirable when live product is packaged and shipped. In addition to the feature of breathability, many current products shipped on pallets need special consideration for product preservation. The areas of most concern are products that need refrigeration, products produced and packaged hot that need to cool at ambient temperature without trapping moisture such as baked goods, chemically treated material that needs to release the chemicals before sale such as surgical gloves and anesthetics and products packaged and cooled rapidly, such as ice cream, yogurt and frozen turkeys. Most manufacturers and shippers of such products need a method of unitizing a pallet load of material, while retaining the properties of ventilation and breathability. Manufacturing operations handling such products function more efficiently if pallet loads are unitized immediately off the production line, before temperature adjustment or the release of gas and moisture. Due to the problems inherent in these specialized manufacturing operations only certain methods of unitization have been found to be acceptable.
In order to retain the required properties of shipping and breathability, various methods have been used which have associated problems.
Some manufacturers use strapping of vertical steel or plastic binding to unitize the product. The problems incurred in the use of strapping are the requirement of costly corner protectors, danger of bending or snapping and injuring the operator while applying this high tension material on the loads and the ever present problem of settling due to moisture wetting the cartons and the sides bulging or normal vibrations causing the straps to loosen and the load to come apart.
Glue is an alternative method used in some areas but customer dissatisfaction with gluing is high because of the problem that taking cartons or bags off the unitized load tends to tear outside layers of the cartons. Glue, although an inexpensive material, requires interleaving for product orientation requiring more durable and expensive packaging material.
Because of the lack of alternatives of packaging, tape is being used to horizontally bind the top layer of the load. However, tape is expensive and allows relatively free movement of all product surrounded.
Stretch netting per se does an excellent job of unitizing and offers breathability but has sealing problems and the cost per load, at present, is equal if not more expensive than present methods, especially in produce and refrigerated ice products areas.
Some manufacturers do not place unitizing material on their stacked loads. Damage of the loads in shipment and customer dissatisfaction is high with such procedures.
In summary, shippers of specialty items that need load environmental considerations have been forced to pay high prices that are passed on to the consumer or incur multiple damage to the load with all presently used modes of unitization. Stretch wrap cannot be used since the film itself places a barrier between the product and the surrounding area, aiding in the over-ripening, deterioration or high cool down time of these specially treated products.
As an alternative to the aforementioned processes the present inventive process offers packaging speed, reliability of package seal and energy savings in that less energy is required to package the products.
A problem with shrink and cling stretch film packaging, in addition to the fact that the film does not allow a load to breathe is that the primary strength and reliability of the package is determined by the consistent quality of the seal. These seals depend on a careful maintenance of the sealing jaw and are never as strong as the film itself. The time that it takes to make the seals is a limiting factor on the possible speeds of most shrink systems with the additional problem that some stretchable materials, as for example, stretch netting, or narrow film widths cannot be effectively heat sealed.
The present invention uses spiral wrapping machinery to apply the film web to the load in the inventive process.
The use of spiral wrapping machinery is well known in the art. One such apparatus is shown by U.S. Pat. No. 3,863,425 in which film is guided from a roll and wrapped around a cylindrical load in a spiral configuration. A carriage drives the film roll adjacent the surface of the load to deposit a spiral overwrap around the load and returns in the opposite direction to deposit another spiral overwrap around the load. Other spiral wrapping apparatus are described by U.S. Pat. Nos. 3,857,486; 3,549,017; 3,412,524; 3,191,289 and 2,716,315.
It has previously been disclosed in U.S. Pat. No. 3,788,199 to spirally wind tapes in a manner that they overlap each other to provide suitable space there between when breathability is required. In this reference, a heavy duty bag is prepared by spirally winding stretched tapes of synthetic resin in opposite directions, so that they intersect each other to form a plurality of superimposed cylindrical bodies which are bonded together to form a cylindrical network. The spirally wound inner and outer tapes of the super-imposed cylindrical body intersect each other at a suitable angle, depending upon the application intended, the preferred embodiment having substantially equal longitudinal transfer strength. In this preferred embodiment the tapes intersect each other an an angle of about 90.degree.. The angle defined by the tapes constituting the cylindrical network may be determined by varying the interrelationship between the travelling speed of the endless belts carrying the tape and the rotating speed of the bobbin holders, which rotate a plurality of tape bobbins to deposit the tape onto the moveable belt. The previously indicated patents rely on heat shrink material, adhesives, a heat seal or the tacky nature of the film to hold the outer layer of wrap in a fixed position.
The turntable clamping assembly described in this specification is disclosed in U.S. Pat. No. 4,077,179. Various patents have described the use of mechanisms for wrapping materials. In U.S. Pat. No. 3,003,297 a complex cutting and holding mechanism is used to place tape on a box and cut it off with the process being repeated for each box.
U.S. Pat. No. 2,088,133 discloses a reverse wrapping wire tying machine. In the reference a gripper mechanism holds a band in position with respect to the load to be wrapped and a rotatable ring drive rotates the band around the load until the band has completed more than one wrap of the load and passes over the body of the gripper mechanism. A separator slide is used to separate the leading edge of the band from the underlying band and a second gripper mechanism attaches to the separate band. A heat sealing mechanism welds the wrapped layer band to the band underneath it and a cutting mechanism severs the leading edge of the band held by the second gripper mechanism which then becomes the trailing edge of the succeeding wrap. When the band is severed the ring drive mechanism is rotated in a reverse direction for the following load with the various gripping and cutting mechanisms functioning in the same manner.
Additional references of interest which are pertinent to rotatable drives for wrapping packages are disclosed in U.S. Pat. Nos. 3,820,451; 3,331,312; 3,324,789; 3,309,839; 3,207,060; 2,743,562; 2,630,751; 3,330,629; 2,054,603; and 2,124,770.
Other applications in packaging are shown by U.S. Pat. Nos. 3,514,920 and 3,793,798 in which heat shrink film is wrapped around a pallet supporting a plurality of cartons. A similar full web apparatus using a tensioned cling film is shown by U.S. Pat. No. 3,986,611 while another apparatus using a tacky PVC film is disclosed in U.S. Pat. No. 3,795,086.
The present invention uses stretchable plastic film in its preferred embodiment since the mechanical stretching of the film utilizes its strength better than heat shrink wrap and at less cost than netting, and can be used on loads where breathing is necessary or no heat can be applied to the product. The elasticity of the collapsed film holds the products under more tension than either shrink wrap or kraft wrap particularly with products which settle or relax when packaged.
It can thus be seen that the problem has been attempted to be solved by various methods and operations, none of which have been entirely satisfactory.